They're great depending on the horse...but be careful. I started using mine on my stocky QH who has no withers, and it actually did more harm than good
It was too much cushion underneath the saddle and made a saddle that fit perfectly fine on her not fit at all. It ended up rubbing all the hair off on both sides under the panels!
I have since stopped using it and gone back to just a plain old AP saddle pad, and the hair is growing back now, no more rubbing. So definitley depends on the horse, some just don't need the extra cushion and it can actually cause fit issues with your saddle!